The present invention relates generally to electric switches, and in particular to an electric switching apparatus such as a cam switch having a driving mechanism, a stop chamber unit and at least one switch chamber unit, each of the units having modular structure axially connectable to the driving mechanism.
An electric switching apparatus of this type designed for installation in an opening of a supporting plate, is known from the German publication No. 2,609,473. This known apparatus has a front part provided with a tubular neck having an outer thread and being insertable from the outside into the opening of the supporting plate up to a stop surface whereupon the neck is secured to the supporting plate by means of a counteracting annular nut applied on the threaded neck from the inside. In order to connect to the front part a block containing the electrical component part, the tubular neck is formed with two juxtaposed segments provided respectively on their free ends with arresting projections which are engageable with corresponding arresting grooves in the block. For this purpose the face of the block which is to be connected to the front part is provided with two openings corresponding in form to the cross section of the segments on the neck so that upon plugging the coupling segments of the front part into these openings the arresting projections on the segments engage the arresting grooves in the block. Transversely to the longitudinal central axis of the block there is also provided a guiding space including a transversely shiftable locking strap which engages the segments and holds the same in a fixed position in the block.
The disadvantage of such prior art switching apparatus is the fact that in order to shift the locking strap from one side into its locking position in contact with the arresting pieces and vice versa to release this locking strap in order to enable the disassembly of respective component parts, a relatively large space is necessary at lateral sides of the apparatus. Another substantial disadvantage of this prior art apparatus also resides in the fact that the segments formed on the tubular sleeve of the front part have to be introduced into the correspondingly shaped guiding openings in the front wall of the block and consequently both the segments and the arresting points cannot be observed and controlled from the outside. In other words, in the assembled condition of the switching apparatus it is impossible to reach the arresting pieces or to control the same, which means they cannot be checked in their arresting position, nor released from the outside from this arresting position. The laterally shiftable locking strap is therefore always necessary to ensure the arresting position of the front part and the block. As a consequence, a cumbersome manipulation is necessary during the assembly of individual component parts of the switching apparatus on the one hand and a relatively complicated design of the apparatus is necessary on the other hand.